Itch leads to serious impairment of quality of life?often times on par with pain. Itch is the hallmark symptom and primary driver of morbidity for atopic dermatitis (AD)?one of the most common inflammatory skin diseases affecting 24 million adults and 10 million children in the U.S. Currently, there is a severe lack of objective measurement of itch. Psychometric surveys are point measurements that lack sensitivity and validity?particularly in children. Measuring itch-related scratching behavior offers a potential objective way to measure itch. Unfortunately, wrist strapped electronics fail to capture scratch accurately and are not adapted for children. This project seeks to accelerate the full qualification of a novel, wearable sensor leveraging a machine learning algorithm to objectively and accurately measure scratching. We propose to address key comments from the FDA in our accepted letter of intent (DDT COA #000120) by accomplishing the following specific aims. Aim 1: we will augment our current scratch sensor to achieve 7-day battery life on a single wireless charge (current battery life: 24 hours) to increase adherence and reduce user burden. Aim 2: we propose to extend healthy normal testing to strengthen our predictive algorithm and train against additional cofounders with an additional 8 subjects (n=16 total). In addition, we will improve the usability and cybersecurity of our software and cloud system. Aim 3: we will extend our existing clinical study at Northwestern University to include more pediatric and adult individuals with AD (n=30 target total). Psychometric surveys will assess user/caregiver experience afterwards, and determine which features of the sensor have greatest value to patients. Success will be defined by successful submission of a full qualification plan to the FDA within 12 months as a fully accepted drug discovery tool. The long- term goal is to make this scratch sensor widely available to support drug development by providing an objective endpoint for itch, and inform future clinical care of treatment response in a patient?s naturalistic environment. Further applications include deployment in other itchy conditions (e.g. prurigo nodularis, chronic pruritus of the elderly, pruritus associated with renal or hepatic failure).